Gaseous discharge device circuit



Feb- 24, 19 G H. ROCKWOOD,'JR 2,273,993

GASEOUS DISCHARGE DEVICE CIRCUIT Filed July 5 1940 a s FILLEQ 3/ v o a a:

ATMOSPHERIC FREESURE SW] GREATER THAN ATMOSPHERIC PRESSURE lNl/EN 70/? G. H ROCK WOOQ JR.

M 32ml Q ram/Er process.

Patented Feb. 24, 1942 GASEOUS DISCHARGE DEVICE cmcUrr George H. Rockwobd, Jr., Summit,' N. 1., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application July 3, 1940, Serial No. 343,755 3 Claims. (Cl. 23083) This invention relate to gaseous discharge device circuits, and, more particularly, to process control circuits or systems.

There frequently arises in industrial or experi mental process control the problem of keeping an indicator, such as a mercury manometer or a moving pointer, between a pair of index marks action of the process, or regulative of the pertions of the cycle of operations involved in the Such an arrangement requires that the circuit shall initiate a reversal of function upon momentary conductive engagement with one contact, but shall be unaffected by the'immediate cessation of such conductive engagement. i

An object of the invention is to enable in any type of process control where there is a necessity to reverse the direction of movement of a moving object, a more reliable control and a simplified control circuit.

In accordance with the invention, the control circuit comprises a gaseous discharge device having a cathode, input control electrode and anode,

with a load and a source of low-voltage, low-fre- -or contacts definitive of the limits of motion or and) through the latter to conduit or tube 23 leading to the vessel at B. The bulb or receptacle 20 which is open to the atmosphere, connects tlfrough tube 2| with the expansion joint 19, and collects the mercury that .spills over from the bulb l5 when the pump is in operation.-

The elbow 22 collects a small amount of the mercury spilled over on the first cycle of the pumps operation, or may be provided initially, to pro- 1 vide a seal against gas flowing back from B or against impairment of the vacuum established in bulb l5 and tube 16 when the pump is in op .eration. The interior of the bulb I3 is connected through tube 24 and the" double valve 25 to a source of atmospheric pressure or to one of greater than atmospheric pressure through the valves 26,21, respectively. The closure member forthe double valve 25 comprises the. plunger or core 28 of the solenoid .29, the normal, i.-e., nonoperated', position of the plunger being such tubes l6, I8 of the pump and extend across the quency, current in series with the cathode and I anode; a fluid or mechanical limit switch comprising a movable conductor, for example, mercury, and a plurality of contacts or terminals for conductive engagement with or by the movable conductor; and connections between the contacts 'andthe electrode andcathode; including networks of preassigned time-constants that de- A more complete understanding of the invention will be obtained from the detailed descrip tion that follows read with reference to the appended drawing, the single figure 'of which shows a pump whose cycle of operations isv controlled by a circuit in accordance with the invention.

The single figure of the drawing discloses an embodiment of the invention. The circuit'ar- I rangement l0 controls the operation of a Toepler pump" I I. Such a pump is of the type in which mercury, or some other liquid, is used as a medi-- um for displacing gas or material to be pumped from one vessel, for example, at A, to another,

for example, at B. and that utilizesliquid valves or seals.

The. pump comprises a bulb or receptacle l3j for mercury I, connected to a second bulb or receptacle l5 by the tube ,l6'to which tube or bore thereofso that the mercury H, in its normal or initial position'in the tube l6, conductively engages with the terminal 3, and on operation of the pump, is adapted to conductively charge device 30 comprising a cathode 3l, an -input control electrode 32 and a plate or anode 33'. A high resistance r is connected between engage with terminals I, 2. I 1

The control circuit comprises a gas-filled disthe grid and cathode. A comparatively 7 all resistanceRi is connected in series with the d biasing battery C'and the control grid. The

cathode isconnected to ground, to terminal 3, and through condenser C1 to the positive terminal of battery 0. A high resistance R: is 'con-' nected between the terminal 2 'and the terminal through the solenoid 29, a low resistance R4, and a source S of low-voltage, low-frequency alternating current to ground. The solenoid 'may be by-passed by a condenser C2. In one arrangement constructed inaccordance with this invention; the components had the following R4: '100 ohms S=110'V., C. P. S;

' Normally open switches SWI and SW2 are conconduit, I! from the vessel at A is connected.

Overflow conduit or tube 18, which maybe a capillary, connects bulb IE to expansion joint I9 nected between the anode and the source Sand between the terminal T and battery'C, respectively. I

With switch SWI open, atmospheric pressure the anode.

is normally acting on the surface of mercury M andthe latter assumes the position in the tube I was; shownv in the drawing; with SW2 open the' condenser C1 cannot be charged by the battery C through resistances R1 and 1'. When it is desired 5 to operate the pump, switch SW2 is closed en-- abling condenser C1 to charge up to a value equa andopposite to that of battery C, thereby .reducing the bias .on the control grid to a point "that positive potential on the anode will cause the tube to discharge or ionize and thegrid to. lose control of the plate current. Closure of SWI connects the alternating current power supply to On the first positive half-cycle,.the tube becomes conducting, valve 26 is closed and valve 21 is opened, connecting the interior'of the bulb l3 to a source of pressure greater than atmospheric. This results in the mercury rising to engage with contact 2. Once conduction has started the tube remains conducting because of i the time-constant of R2 01; during the halfnegative or discharge control potential on succeeding-positive hall-cycles of the anode potential, until the mercury is forced up tube I6, into bulb I5 and out through tube l8 and into con- -ductive engagement with contact I. When the latter occurs, the network R3C1 controls and its time-constant is too small to permit the condenser C1 to retain its charge during the halfcycle whenthe anode is negative. Consequently the. grid is again in control pn the succeeding positive half-cycle,'and the tube deionizes. The plunger '28 returns to its initial position, opening valve 26 and closing valve 21 to connect the bulbl3 interior with a source of atmospheric pressure. The mercury will return to its original level producing a vacuum as it descends.v The gas or other material to be transferred from A to B will be drawn into the tube I6 and bulb 15 as the mercury descends below the junction of tubes ,l6, l1. When the mercury level falls below that of contact 2, the operations already described are repeated, with the rising mercury. forcing the gas or other material in tube IBand bulb l5 out through tube l8. Mercury that spills over past the contact I is collected in bulb 20, and the elbow 22 is provided to collect a small amount to provide a seal to preserve the vacuum established by the mercury movement past the contacts I, 2. This cycle of operations continues so long as the switch SWI remains closed.

The single embodiment of the invention that has been described hereinabove is believed at this. time to be a preferred form thereof, but it is to be understood that the invention is not limited thereto but only by the scope of the appended 7 claims.

and an anode; a load and a source of alternating current potential in series with said cathode and anode; means for biasing said input electrode to a potential such that current cannot, flow between said cathode and anode;'.'meanscomprising a condenser for balancing said biasing potential so that said cathode and input electrode are at the same potential wherebydischarge within said device occurs when the anode stant such that the input'grid is biased between successive positive half-cycles of the anode potential to a potential that prevents continued discharge.

'2. In combination, a tubular member, a conductive column adapted to be raised and lowered in said member, a source of atmospheric pressure and of greater than atmospheric pressure, means for applying such pressures alternately to said column whereby. under greater than atmospheric pressure said column rises to a preassigned level in-said tubular member and under atmospheric pressure falls to a preassigned lower level, and means for regulating the intervals for which the respective pressures are efiective on said column, said means comprising a gaseous discharge device, an input circuit for said device including terminal members located in thepath of movement of said column and adapted for conductive engagement therewith, and an out put circuit for said device including said firstmentio'ned means.

3. In combinatiop, a tubular member, a conductive column adapted to be raised and lowered in said member, a plurality of terminals extending through said tubular member and positioned at different levels in the path of movement of said conductive column, a source of atmospheric pressure and of greater than atmospheric pressure, means for applying such pressures alternately tosaid column whereby under greater than atmospheric pressureisaid column is caused to rise tea preassigned level and to engage with all of said terminals and under atmospheric pres- ,sure is lowered to a preassigned level and engages not more than one terminal, and-means for regulating the intervals for which the respective pressures are effective on'said column and .for producing a cyclical alternation in such pressures, said means comprising a gaseous discharge iievice having a cathode, a grid and an anode, an input circuit for said device comprising said terminals, a plurality of resistance-con denser networks of difierent time constants, and a source of biasingpotential for said grid, and

an output circuit for said device comprising a source of alternating current potential and said first-mentioned means. I

GEORGE H. ROCKWOOD, JR. 

